Light emitting diodes (LEDs) are a kind of semiconductor devices that convert the electric power into infrared rays or light using the characteristics of compound semiconductors, in order to exchange signals, or be used as a light source.
Group III-V nitride semiconductors have been spotlighted as core materials for light emitting devices, such as light emitting diodes (LEDs) or laser diodes (LDs), by virtue of their physical and chemical properties.
Since such light emitting diodes do not contain environmentally harmful materials such as mercury (Hg) used for existing lighting apparatuses, such as incandescent lamps or fluorescent lamps, and have long lifespan and low power consumption, the light emitting diodes are a replacement for the existing light sources.
On the other hand, when two layers having different coefficients of thermal expansion are stacked, various stresses, for example shear stresses, may be caused to these layers. That is, when one of the two layers in the conventional light emitting device package forms a light emitting element and the other of the two layers forms a pad, if the pad is bonded to the light emitting element at 200° C. or higher, the initial failure and the cumulative fatigue are generated because of the residual stress due to the different coefficients of thermal expansion between the light emitting device and the pad so that the light emitting device package may be destroyed.